package nbcb;

import java.util.Scanner;

public class E {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int score;
        while (sc.hasNext()) {
            score = sc.nextInt();
            if (score >= 90 && score <= 100) {
                System.out.println("A");
            }else if (score >= 80 && score <= 89) {
                System.out.println("B");
            }else if (score >= 70 && score <= 79) {
                System.out.println("C");
            }else if (score >= 60 && score <= 69) {
                System.out.println("D");
            }else if (score >= 0 && score <= 59) {
                System.out.println("E");
            }else {
                System.out.println("Score is error!");
            }
        }
    }
}
